There are a number of known approaches to determining the presence or amount of a chemical species in a target environment by exposing a substance capable of interacting with the species to such environment and monitoring a change in a property of the substance due to such interaction as an indication of whether or in what amount the species is present.
One such approach has been the exposure to the environment of a species-interactive substance applied to a piezoelectric substrate. The substance is affected such that, if any of the species present, a preselected property of the substance is changed. A surface acoustic wave is induced in the piezoelectric material. Any change of property in the substance results in an attenuation of the surface acoustic wave, which can be monitored as an indication of whether or in what amount the species is present. For instance, see U.S. Pat. Nos. 4,312,228 and 4,759,210.
Another approach has been the provision of a capacitive device for detecting the presence or measuring the concentration of an analyte in a fluid medium. A plurality of interdigitated fingers formed from metallic conductors are placed upon an insulating substrate. The substrate may be made from an insulating material such as glass and the fingers may be made of copper and gold; the fingers are covered with an insulating passivation layer. The approach involves biospecific binding between a biochemical binding system and the analyte to change the dielectric properties of the sensor. See U.S. Pat. No. 4,822,566.
Yet another approach has been the provision of a chemical sensor comprising a thin film of dithiolene transition metal complexes applied to a chemiresistor device. The film is deposited upon an interdigitated electrode on a substrate. The film changes conductivity when exposed to a chemical gas or vapor of analytical interest. The interdigitated electrodes may be gold and the substrate is an insulating material such as quartz. A power supply and current measuring device are included. See U.S. Pat. No. 4,992,244.
Still another approach has been provision of a biosensor in the nature of a sample testing device that includes an electrode structure which makes measurements of one or more electrically measurable characteristics of the sample. The area between two electrodes on one wall of the test cell can be coated with a binding agent which can bind conducting particles such as gold sol particles. See U.S. Pat. No. 5,141,868.
A different type of biosensor which has also been suggested has a thin crystalline drive surfactant polymeric electrically conducting layer to which may be bound members of specific binding pairs. Binding of an analyte or reagent to the binding pair member layer may change electrical properties of the layer for measurement of the analyte. See U.S. Pat. No. 5,156,810.
However, it would still be desirable for the art to have an alternative detection technology which lends itself to ready and versatile implementation as well as consumes power at a very low level, without sacrificing reliability, miniaturization affinity, and low cost.